Improve touch screen and text conversion behavior of many commands

Improve touch screen and text conversion behavior of many commands

* doc/lispref/commands.texi (Key Sequence Input): Document new
argument to `read-key-sequence' etc.
* lisp/help-macro.el (make-help-screen):
* lisp/subr.el (read-key, read-char-choice-with-read-key):
Disable text conversion and display the OSK before reading a key
sequence.
* lisp/touch-screen.el (touch-screen-window-selection-changed):
Only cancel the minibuffer OSK timer.
(touch-screen-handle-point-up): Update comment accordingly.
* src/keyboard.c (command_loop_1, read_menu_command)
(read_key_sequence, read_key_sequence_vs, Fread_key_sequence)
(Fread_key_sequence_vector): New arg DISABLE_TEXT_CONVERSION.
All callers changed.